Integrated circuits can use single-ended signals as well as differential signals. Differential signals are signals that include two components: a true component and a complementary component. The two components of a differential signal have opposite polarities. For example, when the true component is a logical "1," the complementary component is a logical "0." Likewise, when the true component is a logical "0," the complementary component is a logical "1." In contrast to differential signals, single-ended signals are signals having a single component that takes on values of logical "1" and logical "0" with no complementary counterpart.
Differential signals can provide noise immunity and balanced currents that can aid in the operation of high speed circuits. Some circuits that utilize differential signals accept single-ended signals as inputs, and then generate time-aligned differential component signals for use in the circuit. If the two components of a differential signal are not time aligned, high speed operation of circuits can be adversely affected.
FIG. 1 shows a prior art differential signal generator. Differential signal generator 100 includes input node 102, true output node 108, and complementary output node 110. The complementary output is produced by inverter 106, and the true output is produced as a delayed version of the input. Delay 104 functions to compensate for the delay in inverter 106 in an attempt to time-align the differential component outputs. This approach can only time align the outputs within a certain time offset, in part because of manufacturing process variations and device-to-device mismatch between delay 104 and inverter 106. Differential signal generator 100 has a maximum operating frequency determined in part by the time offset between the true and complementary outputs.
For the reasons stated above, and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the present specification, there is a need in the art for an alternate method and apparatus for generating differential signals from single-ended signals.